The amount of energy striking the earth from the sun in just one day is enough to provide electric power for the human race for 175 years at the present rate of consumption. One way to gather some of this energy is through photovoltaic panels; but they turn off when the sun goes down. Furthermore, available photovoltaic panels are expensive compared to the cost of electric power produced by fossil fuels.
Another way to harvest solar energy is to concentrate sunlight with parabolic mirrors to produce steam in a Rankine cycle that generates electric power. But, again, this technique is expensive and labor intensive and is useful only during relatively dear daylight hours. Projects that propose the use of flat panel collectors for the conversion of solar energy to thermal energy for the production of output power have proven uneconomical due to the cost of constructing large areas of collector surfaces. Both of the methods also require some external form of energy storage in order to continue to produce power at night.
Flat solar panels normally are formed in rectangular boxes with one or two layers of glazing above the absorbing surface, and the sidewalls that support the glazing cast shadows on the absorbing surface in early morning and late afternoon. Furthermore, the frames of the boxes provide heat paths, which lose energy from the solar collectors to the ambient air.
What is needed is a system that inexpensively harvests solar energy over large areas, using part of the energy to produce power during the daytime and storing the rest of the energy for nighttime power generation. For example, Brookhaven National Laboratory Report BNL 51482, UC-59c, "The Development of Polymer Film Solar Collectors: A Status Report," W. G. Wilhelm et al., August 1982, describes a solar collector consisting of plastic films that are sealed together at appropriate places by a roller system in a factory. The rolls of plastic film are then cut into sections and mounted into rigid frames. Bottom insulation is applied to reduce heat loss.
A number of patents show the construction of solar panels that consist of plastic films for glazing and for channels containing a heat collecting fluid. U.S. Pat. Nos. 4,038,967, 4,559,924, and 4,597,378 show plastic films sealed together for the transport of heat collecting fluids and plastic films for glazing. In these cases, rigid frameworks are required to support the films and insulation is provided to prevent heat loss below the panels.
U.S. Pat. No. 4,036,209 shows a water channel with walls of plastic and a plastic glazing supported by air pressure. It is attached to a rigid structure and is not designed to cover large areas over the ground. U.S. Pat. No. 3,174,915 is a solar still that uses an air-inflated cover for glazing and for condensate collection. It is attached to a rigid framework. U.S. Pat. No. 3,991,742 describes a water-heater solar panel consisting of two plastic films between which water flows. This system is designed to be attached to a pitched roof to provide the necessary gravity fluid flow.
The present invention, Solar Power and Energy Storage System (SPAESS), provides a solar energy harvest system that can be applied over large ground areas to economically produce electric power from the sun during the daylight and store energy in the underlying earth for nighttime power generation. A square mile (640 acres) of solar harvest can output over a hundred megawatts of power during peak demand in the daytime and continue to generate energy at relatively high levels during the night when the demand for electricity has decreased.
Various objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.